Medullary cavity

The medullary cavity (medulla, innermost part) is the central cavity of bone shafts where red bone marrow and/or yellow bone marrow (adipose tissue) is stored; hence, the medullary cavity is also known as the marrow cavity.

Located in the main shaft of a long bone (diaphysis) (consisting mostly of spongy bone), the medullary cavity has walls composed of compact bone (cortical bone) and is lined with a thin, vascular membrane (endosteum).

Intramedullary is a medical term meaning the inside of a bone. Examples include intramedullary rods used to treat bone fractures in orthopedic surgery and intramedullary tumors occurring in some forms of cancer or benign tumors such as an enchondroma.